A stone is allowed to fall down from the top of a tower 100m high

A stone is allowed to fall down from the top of a tower 100m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 ms-1. Calculate when and where the two stones will meet? (take g = 10ms-2)

Let a stone A is allowed to fall from top of a height h = 100m
Its initial velocity u1 = 0
And a1 = +g = +10 ms-2
Another stone B is projected upwards from the ground with an initial velocity u2 = 25ms-1 and for it a2 = -g = -10 ms-2
Let the two stones meet at a point C at a distance y below A or (100-y) above B after a time t.
Then for stone A
image
For stone B
image